Method of making molybdenum and high temperature oxidation resistant alloy laminatedcomposite material



Aug. 24, 1965 E. D. SAYRE 3,

METHOD OF MAKING MOLYBDENUM AND HIGH TEMPERATURE OXIDATION RESISTANT ALLOY LAMINATED COMPOSITE MATERIAL L Original Filed March 17, 1960 Z N/L'f/fO/WA Jr /0 l2 M04 YBO'Nt/M fluoy ,4 A/IC/l/fO/V' I 2 2 :1 K ANCHIEOM' .Y /2 (M04 Yeas/van 1744 a y A mlcmeome JZ' INVENTOR.

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United States Patent 3,201,863 METHOD OF MAKING MOLYBDENUM AND HIGH TEMPERATURE OXIDATION RESISTANT ALLOY LAMINATED COMPOSITE MATERIAL Edwin D. Sayre, Richland, Wasln, assignor to the United This invention relates to the method for making the herein disclosed improved means for inhibiting the oxidation of molybdenum and molybdenum based alloys at high temperatures and under corrosive atmospheric Conditions. This application is a division of application Serial No. 15,773, filed March 17, 1960, to the article that on January 7, 1964, issued as Patent No. 3,116,981.

Molybdenum and molybdenum based alloys which are in the class of the so-called refractory metals have a great potential in aircraft gas turbine designs because of their high strength at elevated temperatures. However, their very poor oxidation resistance renders them useless above 800 F.

Methods presently employed consist of making the part, such as a turbine bucket by forging and machining the alloy and applying a protective metallic or ceramic coating or cladding. In the advent of failure of this coating or cladding, the base metal alloy is exposed to oxygen and reacts to form volatile oxides which cause a considerable loss of the base metal and ultimately the failure of the part.

An object of this invention is to combine in laminated structures a base metal consisting of molybdenum or molybdenum alloy alternated with a high temperature oxidation resistant alloy such as Nichrome V to provide a material Which is highly resistant to oxidation at high temperatures.

Another object is to form a laminated body comprising sheets of oxidation resistant material and layers of molybdenum so that if the outside clad of oxidation resistant material fails, only a very thin sheet of molybdenum alloy like.

Other and further objects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawing in which:

The single figure of the drawing shows a fragmentary enlarged sectional view of the composite laminated metal body comprising sheets of oxidation resistant Nichrome V alternated with molybdenum alloy.

Referring to the single figure of the drawing, it can be seen that the composite body 2 comprises alternating sheets of Nichrome V and sheets 14 of molybdenum alloy. The use of the expression molybdenum alloy hereafter is intended to also include as an alternative the metal molybdenum. The metal molybdenum contemplated herein is the element molybdenum of atomic No. 42. The molybdenum alloys referred to herein are alloys of molybdenum with titanium, for example, an alloy that has the composition by weight of 99.5% molybdenum and 0.5% titanium. It is to be understood, however, that the specific composition of the molybdenum alloy is not critical as long as materials of high strength are employed. Refractory metals and alloys which include the metal molybdenum have the advantages, where such characteristics are desirable, of being difficult to fuse, diflicult to reduce, unmanageable and the like.

Nichrome V is a trademark registered to Driver- Harris Co. of Harrison, New Jersey for an alloy that consists of by weight Ni and 20% Cr, of melting point 2550 F., specific gravity 8.41 and a tensile strength of from 100,000 to 200,000 pounds per square inch. 7

The total volume of molybdenum illustratively is not less than two-thirds the volume of the laminated metal composite body. The thickness of the internal sheets of Nichrome V or comparable high temperature oxidation alloy is illustrated in the drawing as being small as compared with the thickness of the molybdenum sheets. specific thickness selected should be within the range of 0.001 to 0.01 inch depending on the desired strength of the body.

The preferred embodiment shown in the single figure of the drawing shows all of the sheets 12 of the molybdenum alloy being of equal thickness, preferably 0.005 inch. Nichrome V on the outer surfaces of the composite body are also the same thickness as the molybdenum alloy. However, the inner sheets-14 of Nichrome V are preferably only 0.002 inch thick. As disclosed, the alternating sheets are stacked to a total thickness of 0.050 inch, hot pressed to 0.040 inch and then hot rolled to 0.030 inch.

The hot pressing operation should take place in a sufficiently reducing atmosphere at a satisfactory diffusion welding temperature of the order of 2200 F. The specific temperature and pressure employed in the hot pressing operation are interdependent one upon the other. When the temperature is high, the pressure is accordingly lower than would be necessary if the temperature was low. This is true to the extent that if a high enough pressure is used, the temperature could be at room temperature and a limited amount of difiiusion between the laminas would result. Furthermore, the desired percentage reduction in thickness of the composite body during each rolling operation will be an important factor in determining the specific temperature and pressure to be employed. Suitable atmospheres are provided by hydrogen or disassociated ammonia and suitable inert atmospheres are provided by vacuum or inert gases such as argon and the like. The hot pressed compact is then cold worked to obtain the ultimate desired thickness and properties.

The laminated material made by the above process may be used to fabricate turbine buckets, nozzle diaphragm partitions and other high temperature parts. These parts may also be forged from bar stock made of laminates. In practice, it has been found that design utilization of an air cooled turbine bucket made of laminated molybdenum sheets will perform successfully at turbine inlet temperatures in excess of 2600 F.

It is apparent that in practicing the invention as taught herein, that the edges of the laminated material will need to be protected from oxidation, especially in the area of the molybdenum sheets. The limited oxidation along the edges of the molybdenum sheets may be inhibited by either coating or cladding the exposed edges of the laminated material or where turbine buckets or the like are being fabricated, the edges are welded closed during the fabrication process.

It is to be understood that variations may be made in the examples of techniques without departing from the spirit and scope of the invention.

I claim:

1. A method of making a composite metal body suitable for making gas turbine wheel buckets and the like and characterized by high hot strength and resistance to The oxidation at high temperatures comprisingthesteps of interleaving thin sheets of molybdenum with thin sheets i of a nickel chromium alloy, the molybdenum sheets having a thickness atleast twice the thickness of the'nickel chromium alloyj sheets, the stackof interleaved sheets.

beginning and ending with a nickel chromium sheet, heating the stackof interleaved sheets to a temperature of the order of 2200 in a reducing atmosphere, and while so heated .applyingsufli'cient pressure normal .to the stackedsheets to reduce the'stack thickness by'the order of twenty percent of the original,thickness whereby the metalshe'ets willfbecomedifiusion welded to form a com-v po'site'bod'y capable of being employedas forging stock and for hot rolled "sheet. 7 V

2. The process of making the laminated metal'body that e'flectually res'ists oxidation for a prolonged period. of

time at zoooP'F. comprising a plurality offlthin sheets of order, the stack of interleaved sheets beginning and end ing with a nickel-chromiumgsheet, and hot pressing the stacked sheets with interdependent temperature and pressure adequatefor accomplishingvdiffusion between c0n- 5 tacting laminas of the stacked sheets.

3. The process defined by the above claim 2 with the hot pressing operationtaking place in a reducing atmosphere at a diffusion'welding temperatureof'the order of about 2 200 F.- accomplishing diffusion between con- 10 tasting Ia'minas of the stacked sheets that are being hot pressed," V v V p 4. The'p rocess' definedby the above claim 2 wherein theshee'ts are stacked to a total thickness 'of 0.050 inch,

15 inch thickness.

nickeLchromium alloy alternatedwith and welded to adjacent thicker sheets of molybdenum andthe metal body 7 References Cited by the Examiner UNITED STATES PATENTS 1 hot'pressed to 0.040inch.thickness, andhot rolledvto 0.030' 

1. A METHOD OF MAKING A COMPOSITE METAL BODY SUITABLE FOR MAKING GAS TURBINE WHEEL BUCKETS AND THE LIKE AND CHARACTERIZED BY HIGH HOT STRENGTH AND RESISTANCE TO OXIDATION AT HIGH TEMPERATURES COMPRISING THE STEPS OF INTERLEAVING THIN SHEETS OF MOLYBDENUM WITH THIN SHEETS OF A NICKEL CHROMIUM ALLOY, THE MOLYBDEUM SHEETS HAVING A THICKNESS AT LEAST TWICE THE THICKNESS OF THE NICKEL CHROMIUM ALLOY SHEETS, THE SSTACK OF INTERLEAVED SHEETS BEGINNING AND ENDING WITH A NICKEL CHROMIUM SHEET, HEATING THE STACK OF INTERLEAVED SHEETS TO A TEMPERATURE OF THE ORDER OF 2200*F. IN A REDUCING ATMOSPHERE, AND WHILE SO HEATED APPLYING SUFFICIENT PRESSURE NORMAL TO THE STACKED SHEETS TO REDUCE THE STACK THICKNESS BY THE ORDER OF TWENTY PERCENT OF THE ORIGINAL THICKNESS WHEREBY THE METAL SHEETS WILL BECOME DIFFUSION WELDED TO FORM A COMPOSITE BODY CAPABLE OF BEING EMPLOYED AS FORGING STOCK AND FOR HOT ROLLED SHEET. 